JP2011106513A - Hydraulic control device for cargo handling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic control device for cargo handling capable of preventing a cylinder from moving down in opening an on/off-valve, in a hydraulic control device for cargo handling including a solenoid valve opening and closing a working fluid conduit for connecting a hydraulic cylinder for cargo handling and a hydraulic pump for cargo handling. <P>SOLUTION: A main controller 40 brings a solenoid valve 32 for lift into a closed state when an operation amount θ of a lift lever 22 by a potentiometer 42 is in a preset dead zone, and brings the solenoid valve 32 for lift into an open state when the operation amount θ of the lift lever 22 is not in the dead zone. The main controller 40 controls a revolution number of a pump motor 31 for lift to be a holding revolution number according to a load W by a pressure sensor 44 when the solenoid valve 32 for lift is changed from the closed state to the open state. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydraulic control device for cargo handling.

  The speed control of the hydraulic cylinder for forklift handling is performed by controlling the flow rate of hydraulic oil flowing to the cargo handling cylinder with the spool of the control valve, but it is directly controlled by the rotation speed of the hydraulic pump to improve efficiency and operability. There is something to do (hydraulic servo). However, since the hydraulic pump has oil leakage, there is a problem in the holding method especially when the cylinder is stopped. For this reason, the hydraulic pump is shielded only by the electromagnetic valve (for example, Patent Document 1).

JP 58-193909 A

However, when the weight of the load placed on the fork is heavy, the operation becomes unstable, for example, when the solenoid valve is opened, the cylinder is temporarily lowered due to oil leakage from the pump.
SUMMARY OF THE INVENTION An object of the present invention is to provide a cargo handling hydraulic control apparatus equipped with an on-off valve for opening and closing a hydraulic fluid flow path connecting a hydraulic cylinder for cargo handling and a hydraulic pump for cargo handling. An object of the present invention is to provide a hydraulic control device for cargo handling that can be prevented.

  According to the first aspect of the present invention, a cargo handling operation member operated to perform cargo handling, a fixed displacement type cargo handling hydraulic pump, and a cargo handling hydraulic pressure operated by a working fluid supplied from the cargo handling hydraulic pump. A cylinder, an on-off valve that opens and closes a flow path of the working fluid connecting the hydraulic cylinder for cargo handling and the hydraulic pump for cargo handling, an operation amount detection means for detecting an operation amount of the operation member for cargo handling, A load detecting means for detecting the load of the load of the cargo, and when the operation amount of the cargo handling operation member by the operation quantity detection means is in a preset dead zone, the on-off valve is closed and the cargo handling operation is performed When the operation amount of the member is not in the dead zone, the on-off valve control means for opening the on-off valve, and the load detection when the on-off valve control means changes the on-off valve from the closed state to the open state. And gist that and a pump control means for controlling the rotational speed of the hydraulic pump for loading and unloading so that the holding rotational speed according to the load by means.

  According to the first aspect of the present invention, the on-off valve control means closes the on-off valve when the operation amount of the cargo handling operation member by the operation amount detection means is in a preset dead zone, and When the operation amount of the operating member is not in the dead zone, the on-off valve is opened. When the opening / closing valve is changed from the closed state to the open state by the opening / closing valve control means, the number of rotations of the cargo handling hydraulic pump is controlled by the pump control means so that the holding rotation number according to the load by the load detection means is obtained. The

Therefore, when the on-off valve is opened, since the rotation speed of the cargo handling hydraulic pump is controlled to be the holding rotation speed corresponding to the load, it is possible to prevent the cylinder from descending.
According to a second aspect of the present invention, in the cargo handling hydraulic control device according to the first aspect, the holding rotational speed is a minimum rotational speed capable of holding the position of the load.

According to the invention described in claim 2, it is possible to prevent the cylinder from descending with a small amount of energy.
3. The cargo handling hydraulic control apparatus according to claim 1 or 2, wherein the pump control means starts rotation of the cargo handling hydraulic pump when the dead zone is exceeded, and the on-off valve control means. The opening / closing valve may be opened when the rotation speed of the cargo handling hydraulic pump reaches the holding rotation speed.

  In the invention according to claim 4, a cargo handling operation member operated to perform cargo handling, a fixed displacement type cargo handling hydraulic pump, and a hydraulic pressure for cargo handling operated by a working fluid supplied from the cargo handling hydraulic pump. A cylinder, an on-off valve that opens and closes a flow path of the working fluid that connects the cargo handling hydraulic cylinder and the cargo handling hydraulic pump, an operation amount detection means that detects an operation amount of the cargo handling operation member, and the operation On-off valve control means for closing the on-off valve when the operation amount of the cargo handling operation member by the amount detection means is in a preset dead zone, and opening the on-off valve when not in the dead zone And a load detection means for detecting the load of the cargo for cargo handling, and when the operation amount of the cargo handling operation member by the operation quantity detection means is in the dead zone, according to the load by the load detection means And pump control means for controlling the hydraulic pump for loading and unloading so that the holding torque output, and summarized in that with a.

  According to the fourth aspect of the present invention, the on-off valve control means closes the on-off valve when the operation amount of the cargo handling operation member by the operation amount detection means is in a preset dead zone, and the dead zone. When it is not, the on-off valve is opened. Further, when the operation amount of the operation member for cargo handling by the operation amount detection means is in the dead zone, the hydraulic control pump for cargo handling is controlled by the pump control means so that a holding torque output corresponding to the load by the load detection means is obtained.

Therefore, when opening the on-off valve, the cargo handling hydraulic pump is controlled to output a holding torque according to the load, so that the cylinder can be prevented from descending.
According to a fifth aspect of the present invention, in the cargo handling hydraulic control apparatus according to the fourth aspect, the holding torque output is a minimum torque output capable of holding the position of the load.

According to the invention described in claim 5, it is possible to prevent the cylinder from descending with a small amount of energy.
The cargo handling hydraulic control device according to claim 4 or 5, wherein the pump control means is configured such that the operation amount of the cargo handling operation member by the operation quantity detection means is not in the dead zone. The load handling hydraulic pump may be controlled so as to have a rotational speed corresponding to an operation amount of the load handling operation member by the operation amount detection means and a load by the load detection means.

  According to the present invention, in a hydraulic control apparatus for cargo handling provided with an on-off valve for opening and closing a hydraulic fluid flow path connecting a hydraulic cylinder for cargo handling and a hydraulic pump for cargo handling, the cylinder is lowered when the on-off valve is opened. Can be prevented.

The side view of a forklift. The circuit diagram which shows the hydraulic and electrical structure of the hydraulic control apparatus for cargo handling of 1st Embodiment. The flowchart for demonstrating the effect | action in the hydraulic control apparatus for cargo handling of 1st Embodiment. The time chart for demonstrating the effect | action in the hydraulic control apparatus for cargo handling of 1st Embodiment. The map which shows the relationship between the load in the hydraulic control apparatus for cargo handling of 1st Embodiment, and threshold value rotation speed. Explanatory drawing which shows the relationship between the operation amount and command rotation speed in the hydraulic control apparatus for cargo handling of 1st Embodiment. The circuit diagram which shows the hydraulic and electrical structure in the hydraulic control apparatus for cargo handling of 2nd Embodiment. The circuit diagram which shows the hydraulic and electrical structure of the hydraulic control apparatus for cargo handling of 3rd Embodiment. The flowchart for demonstrating the effect | action in the hydraulic control apparatus for cargo handling of 3rd Embodiment. The time chart for demonstrating the effect | action in the hydraulic control apparatus for cargo handling of 3rd Embodiment. The map which shows the relationship between the load and torque command value in the hydraulic control apparatus for cargo handling of 3rd Embodiment. Explanatory drawing which shows the relationship between the operation amount and command rotation speed in the hydraulic control apparatus for cargo handling of 3rd Embodiment. The circuit diagram which shows the hydraulic and electrical structure in the hydraulic control apparatus for cargo handling of 4th Embodiment.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the body frame 12 of the forklift 11 is provided with a mast 13 at the front thereof. The mast 13 includes a pair of left and right outer masts 13a supported so as to be tiltable with respect to the vehicle body frame 12, and an inner mast 13b equipped inside the mast 13 so as to be movable up and down. On the rear side of both outer masts 13a, a lift cylinder 14 as a hydraulic cylinder for cargo handling is fixed in parallel with the outer mast 13a, and the tip of the piston rod 14a is connected to the upper part of the inner mast 13b.

  A lift bracket 15 is mounted inside the inner mast 13b so as to be movable up and down along the inner mast 13b. A fork 16 is attached to the lift bracket 15. A chain wheel 17 is supported on the upper part of the inner mast 13b, and a chain 18 having a first end connected to the upper part of the lift cylinder 14 and a second end connected to the lift bracket 15 is hung on the chain wheel 17. Yes. Then, the fork 16 is moved up and down together with the lift bracket 15 via the chain 18 by the expansion and contraction of the lift cylinder 14.

  A base end of a tilt cylinder 19 as a cargo handling hydraulic cylinder is rotatably supported on both the left and right sides of the body frame 12, and a tip end of the piston rod 19a is rotatably connected to a substantially central portion in the vertical direction of the outer mast 13a. ing. The outer mast 13 a is tilted by the expansion and contraction of the tilt cylinder 19.

  A steering lever 21 and a lift lever 22 and a tilt lever 23 as a cargo handling operation member operated to perform cargo handling are respectively provided at the front portion of the cab 20. In FIG. 1, the levers 22 and 23 are shown in an overlapped state. By operating the lift lever 22, the lift cylinder 14 is expanded and contracted and the fork 16 is moved up and down. Further, the tilt cylinder 19 is expanded and contracted by the operation of the tilt lever 23, and the outer mast 13a is tilted.

  In the lift lever 22, there is a region (dead zone) where the lift cylinder 14 does not operate (does not expand or contract) even when the lift lever 22 is operated. The tilt lever 23 also has a region (dead zone) in which the tilt cylinder 19 does not operate (extends or contracts) even when the tilt lever 23 is operated.

The circuit configuration of the cargo handling hydraulic control device for driving the lift cylinder 14 will be described with reference to FIG.
A lift hydraulic pump 30 as a cargo handling hydraulic pump that supplies hydraulic oil as a working fluid in the lift oil tank 34 to the lift cylinder 14 is a lift pump motor as a cargo handling pump motor that uses a battery (not shown) as a power source. It is driven by 31. The lift hydraulic pump 30 is a fixed displacement hydraulic pump, and the lift pump motor 31 is a variable speed pump motor capable of changing the rotation speed. The rotational speed of the lift pump motor 31 is adjusted based on a command signal to the motor controller 41.

  The lift hydraulic pump 30 is connected to a lift solenoid valve 32 as an on-off valve via a conduit 33a, and the lift solenoid valve 32 is connected to the bottom chamber 14b of the lift cylinder 14 via a conduit 33b. A tank 38 is connected to the pipe line 33a via a branch pipe line 33d, and a relief valve 37 is provided in the branch pipe line 33d.

  The supply passages for connecting the lift hydraulic pump 30 and the lift cylinder 14 are formed by the conduits 33a and 33b, and a lift as an on-off valve is provided on the supply passages (the conduits 33a and 33b). An electromagnetic valve 32 is provided. The lift solenoid valve 32 can open and close the hydraulic oil passages (the pipes 33a and 33b).

  When hydraulic fluid is supplied from the lift hydraulic pump 30 to the bottom chamber 14b in a state where the lift solenoid valve 32 is switched to the open state, the lift cylinder 14 is extended. That is, the lift cylinder 14 is operated by the hydraulic oil supplied from the lift hydraulic pump 30. Further, when the hydraulic oil is discharged from the bottom chamber 14b to the lift oil tank 34 with the lift solenoid valve 32 switched to the open state, the lift cylinder 14 is contracted. Further, in the state where the lift solenoid valve 32 is switched to the closed state, fluctuations in the flow rate of the hydraulic oil in the lift cylinder 14 are prevented, and the stop position, that is, the cylinder position is maintained without the lift cylinder 14 contracting. It has become so.

  In the state where the lift solenoid valve 32 is switched to the closed state, the lift hydraulic pump 30 can be connected to the tank 36 via the conduit 33c, and a relief valve 35 is provided in the middle of the conduit 33c. ing. As a result, when the lift solenoid valve 32 is in the closed state, the lift hydraulic pump 30 can be driven to supply hydraulic oil to the tank 36 via the relief valve 35.

  The cargo handling hydraulic control device is provided with a main controller 40, which controls the opening and closing of the lift solenoid valve 32 and also controls the rotation speed of the lift pump motor 31 via the motor controller 41. . The main controller 40 includes a central processing unit (hereinafter referred to as CPU) 40a and a memory 40b. The CPU 40a executes various processes according to predetermined program data stored in the memory 40b. The memory 40b temporarily stores various calculation results of the CPU 40a. Further, the memory 40b stores program data executed by the CPU 40a and various data necessary for the execution.

  A potentiometer 42 that detects an operation amount θ of the lift lever 22 is provided in the vicinity of the lift lever 22. The potentiometer 42 is connected to the main controller 40, and the operation amount θ of the lift lever 22 by the potentiometer 42 is taken into the CPU 40a via an input interface (not shown).

  The lift pump motor 31 is provided with a rotation sensor 43. The rotation sensor 43 is connected to the main controller 40, and the CPU 40a takes in the rotation speed N of the lift pump motor 31 by the rotation sensor 43 via an input interface (not shown).

  A pressure sensor 44 as a load sensor is provided in the pipe line 33b, and the load W is detected by the pressure sensor 44. Specifically, the pressure of the pipe line 33b by the pressure sensor 44 changes when the load (load) is handled by the fork 16, and the pressure of the pipe line 33b corresponds to the weight of the load (load load). Can be detected. A pressure sensor 44 is connected to the main controller 40, and a load W from the pressure sensor 44 is taken into the CPU 40a via an input interface (not shown).

  A motor controller 41 is connected to the main controller 40, and the drive of the lift pump motor 31 is controlled via the motor controller 41. The main controller 40 controls the number of rotations of the lift pump motor 31 based on the amount of operation of the lift lever 22, but by providing a dead zone in the relationship between the lever operation amount and the command motor number of rotations, the noise of the operation amount detection signal This can prevent the motor from starting up frequently. Further, a lift solenoid valve 32 is connected to the main controller 40, and the main controller 40 has a function of controlling opening / closing (ON / OFF) of the solenoid valve 32 based on a sensor signal.

Next, a control method of the cargo handling hydraulic control device, that is, a control method of the lift cylinder 14 will be described.
FIG. 3 is a flowchart for explaining the operation, and FIG. 4 is a time chart for explaining the operation.

  In FIG. 1, it is assumed that the load lever 25 is operated to raise the load 25 on the fork 16 when the load 25 is placed on the fork 16 and is at a predetermined height. In FIG. 4, the lever operation amount θ is increased by the operation of the lift lever 22. As a result, the number of rotations of the lift pump motor 31 increases and the solenoid valve 32 opens.

  In FIG. 3, the CPU 40 a of the main controller 40 takes in the load W at step 100. In step 101, the CPU 40a calculates a threshold rotation speed Nth as a holding rotation speed corresponding to the load W using the map shown in FIG. The map is stored in the memory 40b, and is used to determine the minimum rotation speed (threshold rotation speed) that can hold the position of the lift cylinder 14 with respect to the load W. The map of FIG. 5 has the load W on the horizontal axis and the threshold rotational speed Nth on the vertical axis, and has a characteristic line in which the threshold rotational speed Nth increases as the load W increases. The characteristic lines in FIG. 3 are obtained by actual measurement. Although it is linear in FIG. 3, it is actually non-linear.

  The CPU 40a takes in the operation amount θ of the lift lever 22 and the rotational speed N of the pump motor 31 in step 102 of FIG. In step 103, the CPU 40a determines whether or not the rotational speed N of the pump motor 31 has reached the threshold rotational speed Nth. If not, the process proceeds to step 104. In step 104, the CPU 40a determines whether the operation amount θ of the lift lever 22 is within a specified value θth that defines the dead zone. If the operation amount θ of the lift lever 22 is within the specified value θth, the CPU 40a proceeds to step 105 and outputs a command “0” to the motor controller 41 as the target rotational speed Nt of the pump motor 31. Thereafter, the CPU 40 a closes the electromagnetic valve 32 in step 106.

When the operation amount θ of the lift lever 22 is in the dead zone by the processing of steps 103, 104, 105, and 106, the electromagnetic valve 32 is closed.
When the CPU 40a deviates from the condition that the operation amount θ of the lift lever 22 is smaller than the specified value θth in Step 104, the CPU 40a proceeds to Step 107 and determines that the operation amount θ of the lift lever 22 is equal to the specified value θth (at t1 in FIG. 4). Timing), the process proceeds to step 108. In step 108, the CPU 40a outputs a command for the threshold rotational speed Nth to the motor controller 41 as the target rotational speed Nt of the pump motor 31. The threshold rotation speed Nth is obtained in step 101. Thereafter, the CPU 40a proceeds to step 106.

  When a command for the threshold rotational speed Nth is output as the target rotational speed Nt of the pump motor 31, the rotational speed of the pump motor 31 increases after t1 in FIG. When the lift pump motor 31 is driven while the lift solenoid valve 32 is closed, the hydraulic oil discharged from the lift hydraulic pump 30 is discharged to the tank 36 via the relief valve 35. The relief valve 35 functions as a throttle.

  When the rotational speed N of the pump motor 31 reaches the threshold rotational speed Nth (step t2 in FIG. 4) in step 103 in FIG. 3, the CPU 40a proceeds to step 110 and opens the electromagnetic valve 32.

  In this way, when the lift solenoid valve 32 is changed from the closed state to the open state, the CPU 40a lifts the valve so that the holding rotation speed corresponding to the load W by the pressure sensor 44, that is, the threshold rotation speed Nth is obtained. The number of rotations of the pump motor 31 is controlled. Referring to FIG. 6, the command rotational speed of the lift pump motor 31 when the operation amount θ of the lift lever 22 deviates from the threshold operation amount is as shown in FIG. 5 when the load B is larger than the load A. The threshold rotational speed is large, and the load B is larger than the load A when the command rotational speed in FIG. At this time, the required ascent speed is achieved with the minimum number of revolutions and torque (ie energy consumption). Further, the switching timing from closing to opening of the solenoid valve 32 is shifted as shown in FIG. 4 according to the magnitude of the load.

  After the solenoid valve 32 is opened, the CPU 40a proceeds to step 103 → step 104 → step 107 in FIG. 3, and in step 107, the operation amount θ of the lift lever 22 exceeds the specified value θth. Transition. In step 109, the CPU 40a determines whether or not the electromagnetic valve 32 has been switched to the open state. If the electromagnetic valve 32 has been switched to the open state, the CPU 40a sets the target rotational speed Nt of the pump motor 31 to the motor controller 41 in step 111. A command corresponding to the operation amount θ of the lift lever 22 and the load W is output.

Thereby, after t2 of FIG. 4, it controls so that it may become the rotation speed of the pump motor 31 according to the operation amount (theta) of the lift lever 22, and the load W. FIG.
In this way, the flow rate is controlled only by the rotation speed of the hydraulic pump 30 and the electromagnetic valve 32 for holding the cylinder position is provided, and the load 25 and the fork 16 are provided at the start of the cargo lifting operation (or during fine operation). It is possible to prevent the oil from leaking down due to its own weight. Specifically, it is possible to prevent the fork from temporarily descending at the time of rising when the lift is lifted (or during the fine lifting operation), and to achieve the requested lifting speed. Moreover, even if the load W changes, it can be made the same operation feeling. Furthermore, energy efficiency is good because only the minimum amount of energy required for the required lift is consumed.

  It is more preferable that the pressure sensor signal as the load sensor signal is filtered at an appropriate frequency in order to prevent the command rotational speed from fluctuating due to noise of the pressure sensor signal as the load sensor signal.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The main controller 40 serving as the on-off valve control means, when the operation amount θ of the lift lever 22 as the cargo handling operation member by the potentiometer 42 serving as the operation amount detection means is in a preset dead zone, The valve 32 is closed, and when the operation amount θ of the lift lever 22 is not in the dead zone, the lift solenoid valve 32 is opened. Further, the main controller 40 as the pump motor control means has a holding rotational speed corresponding to the load W by the pressure sensor 44 as the load sensor when the lift solenoid valve 32 is changed from the closed state to the open state. Thus, the rotation speed of the lift pump motor 31 is controlled. Therefore, when the lift solenoid valve 32 is opened, the rotation speed of the lift pump motor 31 is controlled to be the holding rotation speed corresponding to the load, so that the cylinder can be prevented from descending.

  In a broad sense, the main controller 40 as the pump control means is a pressure sensor 44 as a load detection means for detecting the load of the cargo for cargo handling when the lift solenoid valve 32 is changed from the closed state to the open state. What is necessary is just to control the rotation speed of the hydraulic pump 30 as a hydraulic pump for cargo handling so that it may become the holding | maintenance rotation speed according to the load W by. In particular, the main controller 40 as the pump control means and the on-off valve control means starts the rotation of the hydraulic pump 30 when the dead zone is exceeded, and sets the lift solenoid valve 32 when the rotation speed of the hydraulic pump 30 reaches the holding rotation speed. Open it.

(2) Since the holding rotational speed is the minimum rotational speed that can hold the position of the load 25, the cylinder can be prevented from descending with a small amount of energy.
(Second Embodiment)
Next, the second embodiment will be described focusing on the differences from the first embodiment.

In the present embodiment, the present invention is also applied to the tilted cylinder circuit as compared with the first embodiment. This will be described in detail below.
As shown in FIG. 7, a tilt hydraulic pump 50 as a cargo handling hydraulic pump that supplies hydraulic oil as a working fluid in the tilt oil tank 65 to the bottom chamber 19b or the rod chamber 19c of the tilt cylinder 19 is not shown. It is driven by a tilting pump motor 51 as a cargo handling pump motor using a battery as a power source. The tilt hydraulic pump 50 is a fixed displacement hydraulic pump, and the tilt pump motor 51 is a variable speed pump motor whose rotation speed can be changed according to a command signal input to the motor controller 61.

  The tilt hydraulic pump 50 is connected to a first tilt solenoid valve 52 as an on-off valve via a conduit 54a, and the first tilt solenoid valve 52 is connected to the bottom chamber 19b of the tilt cylinder 19 via a conduit 54b. Has been. The bottom chamber 19b is connected to a tank 57 via a branch pipe 54c branched from the pipe 54a, and a relief valve 56 is provided in the branch pipe 54c. On the bottom chamber 19b side, the supply passages for connecting the tilt hydraulic pump 50 and the tilt cylinder 19 are formed by the conduits 54a and 54b, and the first on the supply passages (the conduits 54a and 54b). A tilting solenoid valve 52 is provided. Further, a pressure sensor 63 is provided in the pipe line 54b, and the pressure sensor 63 detects the pressure in the pipe line 54b. The pressure in the pipe line 54b changes as the tilt hydraulic pump 50 is driven, that is, the outer mast 13a tilts and the load (load) is handled by the fork 16, and the pressure in the pipe line 54b changes. It fluctuates depending on the height (load load).

  The tilt hydraulic pump 50 is connected to a second tilt solenoid valve 53 as an on-off valve via a conduit 54d, and the second tilt solenoid valve 53 is connected to a rod chamber 19c of the tilt cylinder 19 via a conduit 54e. It is connected to the. The rod chamber 19c is connected to the tank 59 through a branch line 54f branched from the pipe 54d, and a relief valve 58 is provided in the branch line 54f.

  Then, on the rod chamber 19c side, a supply passage for connecting the tilt hydraulic pump 50 and the tilt cylinder 19 is formed by the pipelines 54d and 54e, and the second on the supply passage (the pipelines 54d and 54e). A tilt solenoid valve 53 is provided. Further, a pressure sensor 64 is provided in the pipe line 54e, and the pressure sensor 64 detects the pressure in the pipe line 54e. The pressure in the pipe line 54e changes when the tilt hydraulic pump 50 is driven, that is, when the outer mast 13a tilts and the fork 16 handles the load (load), and the pressure in the pipe line 54e changes. It fluctuates depending on the height (load load).

  Then, in a state where the first tilt solenoid valve 52 and the second tilt solenoid valve 53 are switched to the open state, the hydraulic oil is supplied from the tilt hydraulic pump 50 to the bottom chamber 19b and the relief from the rod chamber 19c. When the hydraulic oil is discharged to the tank 59 through the valve 58, the tilt cylinder 19 is extended. In the state where the first tilt solenoid valve 52 and the second tilt solenoid valve 53 are switched to the open state, the hydraulic oil is supplied from the tilt hydraulic pump 50 to the rod chamber 19c, and the relief from the bottom chamber 19b. When the hydraulic oil is discharged to the tank 57 through the valve 56, the tilt cylinder 19 is contracted. In this way, the tilt cylinder 19 is operated by the hydraulic oil supplied from the tilt hydraulic pump 50. Further, when the first tilt solenoid valve 52 and the second tilt solenoid valve 53 are switched to the closed state, the flow rate of the hydraulic oil in the tilt cylinder 19 is prevented from changing, and the tilt cylinder 19 does not contract. The stop position is held.

  A known low-pressure priority type shuttle valve 55 is provided between the tilt oil tank 65 and the pipes 54a and 54d, so that the hydraulic oil supplied from the tilt hydraulic pump 50 does not go to the tilt cylinder 19. Further, it is prevented that the oil tank 65 returns directly to the tilt oil tank 65.

  The cargo handling hydraulic control device is provided with a main control controller 60, and the main control controller 60 controls the opening and closing of the tilt solenoid valves 52 and 53, and the rotation speed of the tilt pump motor 51 is controlled via the motor controller 61. Is done. The main controller 60 includes a central processing unit (hereinafter referred to as CPU) 60a and a memory 60b. The CPU 60a executes various processes according to predetermined program data stored in the memory 60b. Further, various calculation results of the CPU 60a are temporarily stored in the memory 60b. Further, the memory 60b stores program data executed by the CPU 60a and various data necessary for the execution.

  In the vicinity of the tilt lever 23, a potentiometer 62 for detecting the operation amount of the tilt lever 23 is provided. The potentiometer 62 is connected to the main controller 60, and the amount of lever operation by the potentiometer 62 is taken into the CPU 60a via an input interface (not shown). The tilt pump motor 51 is provided with a rotation sensor 66. The rotation sensor 66 is connected to the main controller 60, and the CPU 60a takes in the rotation speed of the tilt pump motor 51 by the rotation sensor 66 through an input interface (not shown). Pressure sensors 63 and 64 are connected to the main controller 60, and the difference between the cylinder side pressure and the rod side pressure by the pressure sensors 63 and 64 is taken in as a load W to the CPU 60a via an input interface (not shown).

  A motor controller 61 is connected to the main controller 60, and the drive of the tilt pump motor 51 is controlled via the motor controller 61. Further, the tilting solenoid valves 52 and 53 are connected to the main control controller 60, and the main control controller 60 has a function of controlling the opening and closing (on / off) of the tilting solenoid valves 52 and 53 based on the sensor signal.

Then, the CPU 60a of the main controller 60 executes the process of FIG. Details are as described in the first embodiment, and are omitted here.
As described above, the main controller 60 as the on-off valve control means is used for the tilt when the operation amount θ of the lift lever 22 as the cargo handling operation member by the potentiometer 62 as the operation amount detection means is in a preset dead zone. The solenoid valves 52 and 53 are closed, and when the operation amount θ of the lift lever 22 is not in the dead zone, the tilt solenoid valves 52 and 53 are opened. When the tilt solenoid valves 52 and 53 are changed from the closed state to the open state, the main controller 60 as the pump motor control means holds the number of rotations corresponding to the load W by the pressure sensors 63 and 64 as load sensors. The rotational speed of the tilt pump motor 51 is controlled so that Therefore, when the tilt solenoid valves 52 and 53 are changed from the closed state to the open state, the rotation speed of the tilt pump motor 51 is controlled to be the holding rotation speed corresponding to the load. Can be prevented. As a result, similarly to the lift described in the first embodiment, the rising of the operation can be stabilized with respect to the tilt operation.
(Third embodiment)
Next, the third embodiment will be described focusing on the differences from the first embodiment.

  In this embodiment, the configuration shown in FIG. 8 is used instead of FIG. In FIG. 8, a lift hydraulic pump 70 as a cargo handling hydraulic pump that supplies hydraulic oil as a working fluid in a lift oil tank 74 to the lift cylinder 14 is a cargo handling pump motor that uses a battery (not shown) as a power source. It is driven by a lift pump motor 71. The lift hydraulic pump 70 is a fixed displacement hydraulic pump, and the lift pump motor 71 is a variable speed pump motor capable of changing the rotation speed. The lift pump motor 71 is controlled based on a command signal to the motor controller 78.

  The lift hydraulic pump 70 is connected to a lift electromagnetic valve 72 as an on-off valve via a pipe 73a, and the lift electromagnetic valve 72 is connected to the bottom chamber 14b of the lift cylinder 14 via a pipe 73b. The supply passages for connecting the lift hydraulic pump 70 and the lift cylinder 14 are formed by the conduits 73a and 73b, and the lift passage as an on-off valve is provided on the supply passages (the conduits 73a and 73b). An electromagnetic valve 72 is provided. The flow path (pipe lines 73a and 73b) of the hydraulic oil can be opened and closed by the lift solenoid valve 72.

  When hydraulic fluid is supplied from the lift hydraulic pump 70 to the bottom chamber 14b in a state where the lift solenoid valve 72 is switched to the open state, the lift cylinder 14 is extended. That is, the lift cylinder 14 is operated by the hydraulic oil supplied from the lift hydraulic pump 70. Further, when hydraulic oil is discharged from the bottom chamber 14b to the lift oil tank 74 in a state where the lift solenoid valve 72 is switched to the open state, the lift cylinder 14 is contracted. Further, when the lift solenoid valve 72 is switched to the closed state, the flow rate of the hydraulic oil in the lift cylinder 14 is prevented from changing, and the stop position is maintained without the lift cylinder 14 contracting. Yes.

  The cargo handling hydraulic control device is provided with a main controller 75, and the main controller 75 controls the opening and closing of the lift solenoid valve 72 and the lift pump motor 71. The main controller 75 includes a central processing unit (hereinafter referred to as CPU) 75a and a memory 75b. The CPU 75a executes various processes according to predetermined program data stored in the memory 75b. The memory 75b temporarily stores various calculation results of the CPU 75a. Further, the memory 75b stores program data executed by the CPU 75a and various data necessary for the execution.

  A potentiometer 42 that detects an operation amount θ of the lift lever 22 is provided in the vicinity of the lift lever 22. The potentiometer 42 is connected to the main controller 75, and an operation amount θ of the lift lever 22 by the potentiometer 42 is taken into the CPU 75a via an input interface (not shown).

  The lift pump motor 71 is provided with a rotation sensor 76. The rotation sensor 76 is connected to a motor controller 78, and the rotation speed N of the lift pump motor 71 by the rotation sensor 76 is fed back.

  A pressure sensor 77 as a load sensor is provided in the pipe line 73b, and the load W is detected by the pressure sensor 77. Specifically, the pressure in the pipe 73b by the pressure sensor 77 changes when the load (load) is handled by the fork 16, and the pressure in the pipe 73b corresponds to the weight of the load (load load). Can be detected. A pressure sensor 77 is connected to the main controller 75, and a load W from the pressure sensor 77 is taken into the CPU 75a via an input interface (not shown).

  A motor controller 78 is connected to the main controller 75, and the drive of the lift pump motor 71 is controlled via the motor controller 78. Further, a lift solenoid valve 72 is connected to the main controller 75, and the main controller 75 has a function of controlling on / off of the solenoid valve 72 based on a sensor signal.

Next, a control method of the cargo handling hydraulic control device, that is, a control method of the lift cylinder 14 will be described.
FIG. 9 is a flowchart for explaining the action, and FIG. 10 is a time chart for explaining the action.

  In FIG. 1, it is assumed that the load lever 25 is operated to raise the load 25 on the fork 16 when the load 25 is placed on the fork 16 and is at a predetermined height. In FIG. 10, the operation amount θ is increased by operating the lift lever 22. Along with this, the electromagnetic valve 72 is opened.

In FIG. 9, the CPU 75 a takes in the load W at step 200. In step 201, the CPU 75a takes in the operation amount θ of the lift lever 22.
In step 202, the CPU 75a determines whether or not the operation amount θ of the lift lever 22 is a dead zone. If it is a dead zone, the CPU 75a proceeds to steps 203 and 204. In step 203, the CPU 75 a closes the electromagnetic valve 72, and in step 204, the CPU 75 a calculates a torque that generates a pressure commensurate with the load, and outputs a torque command to the motor controller 78. At this time, the map shown in FIG. 11 is used. This map is stored in the memory 75b and is used to determine the minimum torque output that can hold the position of the load 25. In FIG. 11, the horizontal axis represents the load W, the vertical axis represents the torque command value T, and the characteristic line in which the torque command value T increases as the load W increases. The torque command value T is calculated.

  When the operation amount of the lift lever 22 is in the dead zone by the process of step 204 in FIG. 9, the lift pump motor 71 is controlled so that the holding torque output according to the load is obtained. That is, torque control is performed in the dead zone.

  On the other hand, if the CPU 75a is not in the dead zone in step 202, the CPU 75a proceeds to steps 205 and 206. In step 205, the CPU 75a opens the electromagnetic valve 72. In step 206, the CPU 75a calculates the rotational speed corresponding to the load and the lever operation amount, and outputs a command for the rotational speed to the motor controller 78.

  When the operation amount of the lift lever 22 is not in the dead zone by the process of step 206, the lift pump motor 71 is controlled so as to have a rotational speed corresponding to the operation amount θ of the lift lever and the load W. That is, when there is no dead zone, the rotational speed control is performed.

  Referring to FIG. 12, when the operation amount of the lift lever 22 exceeds the threshold operation amount, the control is switched to the rotation speed control, and a command rotation speed corresponding to the load W and the operation amount θ of the lift lever 22 at that time is calculated. The pump motor 71 is driven at the rotational speed. Therefore, it is possible to prevent the fork from temporarily lowering at the time of rising when the lift is lifted (or during the fine lifting operation), and to achieve the required rising speed. Moreover, even if the load W changes, it can be made the same operation feeling. Furthermore, energy efficiency is good because only the minimum amount of energy required for the required lift is consumed. Further, the relief valve 35 in FIG. 2 is not necessary and a simple circuit configuration can be obtained.

  It is more preferable that the pressure sensor signal as the load sensor signal is filtered at an appropriate frequency in order to prevent the command rotational speed from fluctuating due to noise of the pressure sensor signal as the load sensor signal.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The main controller 75 as the on-off valve control means determines that the operation amount of the lift lever 22 as the operation member for cargo handling by the potentiometer 42 as the operation amount detection means in the processing of steps 202, 203, and 205 in FIG. When the dead zone is set in advance, the solenoid valve 72 as the on-off valve is closed, and when not in the dead zone, the solenoid valve 72 is opened. Further, the main controller 75 as the first pump motor control means outputs a holding torque according to the load W by the pressure sensor 77 as the load detection means when the operation amount of the lift lever 22 by the potentiometer 42 is in the dead zone. The lift pump motor 71 as the cargo handling pump motor is controlled so that Further, the main controller 75 as the second pump motor control means switches the lift pump motor 71 when the operation amount of the lift lever 22 by the potentiometer 42 is not in the dead zone, and the operation amount θ of the lift lever 22 by the potentiometer 42 and Control is performed so that the number of rotations corresponds to the load W by the pressure sensor 77. Therefore, when the electromagnetic valve 72 is opened, the lift pump motor 71 is controlled from the state in which the holding torque output according to the load is output to the rotation amount according to the operation amount of the lift lever 22 and the load. Therefore, it is possible to prevent the cylinder from descending.

  In a broad sense, the main controller 75 as the pump control means is a load by the pressure sensor 77 as a load detection means for detecting the load of the load for cargo handling when the operation amount of the lift lever 22 by the potentiometer 42 is in the dead zone. The lift hydraulic pump 70 as a cargo handling hydraulic pump is controlled so as to obtain a holding torque output corresponding to W. Thus, when the electromagnetic valve 72 is opened, the lift hydraulic pump 70 is controlled to output a holding torque corresponding to the load, so that the cylinder can be prevented from descending. In particular, the main controller 75 rotates the lift hydraulic pump 70 according to the operation amount of the lift lever 22 by the potentiometer 42 and the load W by the pressure sensor 77 when the operation amount of the lift lever 22 by the potentiometer 42 is not in the dead zone. It is good to control so that it may become number.

(2) Since the holding torque output is the minimum torque output capable of holding the position of the load 25, the cylinder can be prevented from descending with a small amount of energy.
(Fourth embodiment)
Next, the fourth embodiment will be described focusing on the differences from the third embodiment.

In the present embodiment, the present invention is also applied to the tilted cylinder circuit as compared with the third embodiment. This will be described in detail below.
In the present embodiment, the configuration is as shown in FIG. 13, and the same components as those in FIG. However, in FIG. 13, the signal of the rotation sensor 66 for detecting the rotation speed of the tilt pump motor 51 is fed back to the motor controller 61 in this embodiment. The main controller 60 shown in FIG. 13 constitutes first and second pump motor control means in this embodiment, and the CPU 60 a of the main controller 60 is connected to the tilt pump motor 51 via the motor controller 61. Is to control. Also in this embodiment, the CPU 60a of the main controller 60 can take in the difference between the cylinder side pressure and the rod side pressure by the pressure sensors 63 and 64 as the load W.

Then, the CPU 60a of the main controller 60 executes the process of FIG. Details have been described in the third embodiment, and are omitted here.
As described above, when the operation amount of the tilt lever 23 as the cargo handling operation member by the potentiometer 62 as the operation amount detection means is in the dead zone, the main controller 60 as the first pump motor control means is the load detection means. The tilting pump motor 51 as the cargo handling pump motor is controlled so that the holding torque output corresponding to the load W by the pressure sensors 63 and 64 is obtained. Further, the main controller 60 as the second pump motor control means switches the tilt pump motor 51 when the operation amount of the tilt lever 23 by the potentiometer 62 is not in the dead zone, and the operation amount and pressure of the tilt lever 23 by the potentiometer 62. It controls so that it may become the rotation speed according to the load by the sensors 63 and 64. FIG. Therefore, as in the lift operation described in the third embodiment, the stability of the operation rising can be obtained with respect to the tilt operation.

The embodiment is not limited to the above, and may be embodied as follows, for example.
In the first, second, third, and fourth embodiments, the load is detected by the pressure sensor, but instead, the load may be detected directly. For example, the load W may be detected using a piezoelectric element.

A throttle may be provided instead of the relief valve 35 in FIG.
In the first embodiment, the rotational speed of the pump motor 31 is monitored, and the pump motor rotational speed reaches the threshold rotational speed (holding rotational speed corresponding to the load) after the lever operation amount shown in FIG. 4 exceeds the dead zone. The on-off valve (solenoid valve 32) was opened. Instead of this, the time from when the lever operation amount exceeds the dead zone is measured, and when the time T1 (see FIG. 4) corresponding to the load elapses, it is assumed that the holding rotational speed is reached and the on-off valve (electromagnetic) The valve 32) may be opened.

  Similarly, in FIG. 4, when the dead zone is exceeded, the on-off valve (solenoid valve 32) may be opened, and at the same time, the rotational speed of the pump motor 31 may be controlled to the holding rotational speed.

  DESCRIPTION OF SYMBOLS 14 ... Lift cylinder, 19 ... Tilt cylinder, 22 ... Lift lever, 23 ... Tilt lever, 30 ... Lift hydraulic pump, 31 ... Lift pump motor, 32 ... Lift solenoid valve, 33a, 33b ... Pipe line, 40 ... Main controller, 40a ... CPU, 42 ... potentiometer, 44 ... pressure sensor, 50 ... tilt hydraulic pump, 51 ... tilt pump motor, 52 ... tilt solenoid valve, 53 ... tilt solenoid valve, 54a, 54b, 54c , 54d ... pipe, 60 ... main controller, 60a ... CPU, 62 ... potentiometer, 63 ... pressure sensor, 64 ... pressure sensor, 70 ... lift hydraulic pump, 71 ... lift pump motor, 72 ... lift solenoid valve 73a, 73b ... pipeline, 75 ... main controller, 75a ... CPU, 77 ... pressure Capacitors.

Claims (6)

A cargo handling operation member operated to perform cargo handling;
A fixed-capacity hydraulic pump for cargo handling;
A cargo handling hydraulic cylinder that is operated by a working fluid supplied from the cargo handling hydraulic pump;
An on-off valve that opens and closes a flow path of the working fluid that connects the cargo handling hydraulic cylinder and the cargo handling hydraulic pump;
An operation amount detection means for detecting an operation amount of the operation member for cargo handling;
Load detecting means for detecting the load of the load for cargo handling;
When the operation amount of the cargo handling operation member by the operation amount detection means is in a preset dead zone, the on-off valve is closed, and when the operation amount of the cargo handling operation member is not in the dead zone, An on-off valve control means for opening the on-off valve; and
A pump for controlling the rotation speed of the cargo handling hydraulic pump so that the rotation speed is maintained according to the load by the load detection means when the on-off valve is changed from the closed state to the open state by the on-off valve control means. Control means;
A hydraulic control device for cargo handling, comprising:   2. The hydraulic control apparatus for cargo handling according to claim 1, wherein the holding rotation speed is a minimum rotation speed capable of holding a position of a load.   The pump control means starts rotation of the cargo handling hydraulic pump when the dead zone is exceeded, and the on-off valve control means opens the on-off valve when the speed of the cargo handling hydraulic pump reaches the holding speed. The hydraulic control device for cargo handling according to claim 1 or 2, characterized in that: A cargo handling operation member operated to perform cargo handling;
A fixed-capacity hydraulic pump for cargo handling;
A cargo handling hydraulic cylinder that is operated by a working fluid supplied from the cargo handling hydraulic pump;
An on-off valve that opens and closes a flow path of the working fluid that connects the cargo handling hydraulic cylinder and the cargo handling hydraulic pump;
An operation amount detection means for detecting an operation amount of the operation member for cargo handling;
An on-off valve that closes the on-off valve when the operation amount of the cargo handling operation member by the operation amount detection means is in a preset dead zone, and that opens the on-off valve when not in the dead zone Control means;
Load detecting means for detecting the load of the load for cargo handling;
A pump control means for controlling the cargo handling hydraulic pump so that a holding torque output according to the load by the load detection means is obtained when the operation amount of the cargo handling operation member by the operation quantity detection means is in the dead zone; ,
A hydraulic control device for cargo handling, comprising:   5. The hydraulic control apparatus for cargo handling according to claim 4, wherein the holding torque output is a minimum torque output capable of holding a position of a load.   The pump control means, when the operation amount of the cargo handling operation member by the operation quantity detection means is not in the dead zone, the cargo handling hydraulic pump, and the operation quantity of the cargo handling operation member by the operation quantity detection means and The hydraulic control device for cargo handling according to claim 4 or 5, wherein the control is performed so that the number of rotations according to the load by the load detection means is set.

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